The body is comprised of two major muscle types, striated and smooth. Striated muscle is comprised of skeletal and cardiac muscle, while smooth muscle is found mainly in the vascular system and in internal organs. Of these two, striated muscle is the most abundant with skeletal muscle, by itself, comprising up to 40% of a human's body mass. In this regard, it is appreciated that skeletal muscle diseases affect millions of people. The diseases include simple loss of muscle mass, as in disuse, age related, as in sarcopenia, diseases caused by structural defects in the muscle such as in muscular dystrophy, or myopathies caused by certain toxins, drugs, radiation therapy, and inflammatory reactions in the body that are directed against the muscle. Muscle atrophy can result from a co-morbidity of several common diseases and contributing factors from other diseases, including cancer, AIDS, diabetes, obesity, radiation, and many others. A reduced quality of life is often the result of muscle atrophy as the ability to perform some tasks decreases and the risk of falling is increased.
Excessive exposure to DNA damaging agents, such as what is encountered during chemotherapy, space travel, radioactive material operation, medical imaging and radiation exposure, welding, and outdoor work can also cause cellular, tissue, and organ damage, including muscle atrophy and injury. For example, NASA has found that astronauts lose up to 20% of muscle mass on spaceflights for 5 to 11 days. Similarly, cancer patients subject to radiation treatments or some types of chemotherapy drugs experience muscle atrophy and dysfunction. Nevertheless, the effect of exposure to DNA damaging agents, such as ionizing radiation, on muscular injury has not been well studied, and effective strategies to reduce the effects of exposure to such radiation remain limited.